Long range Kondo signature of a single magnetic impurity

The Kondo effect, one of the oldest correlation phenomena known in con-densed matter physics [1], has regained attention due to scanning tunnel-ing spectroscopy (STS) experiments performed on single magnetic impurities [2, 3]. Despite the sub-nanometer resolution capability of local probe tech-niques one of the fundamental aspects of Kondo physics, its spatial extension, is still subject to discussion. Up to now all STS studies on single adsorbed atoms have shown that observable Kondo features rapidly vanish with increas-ing distance from the impurity [4, 5, 6, 7, 8, 9]. Here we report on a hitherto unobserved long range Kondo signature for single magnetic atoms of Fe and Co buried under a Cu(100) surface. We present a theoretical interpretation of the measured signatures using a combined approach of band structure and many-body numerical renormalization group (NRG) calculations. These are in excellent agreement with the rich spatially and spectroscopically resolved experimental data. 1 a